In the related art, there is a known gas turbine configured to take air into a compressor and generate compressed air, supply the compressed air into a combustor and combust fuel to generate a combustion gas, cause the combustion gas to pass through a main flow path in which a plurality of turbine vane rows and a plurality of turbine blade rows are alternately disposed, and cause the combustion gas to flow along the axis of a rotary shaft from an upstream side to a downstream side, thereby rotating the rotary shaft.
Here, FIG. 8 shows an example of such a gas turbine 100 (see Patent Literature 1).
As shown in FIG. 8, the gas turbine 100 includes a turbine vane row 21, a turbine blade row 22, a turbine disk 23 to which the turbine blade row 22 is attached, an intermediate shaft cover 24, a support ring 25 fixed to the intermediate shaft cover 24 via a bolt 26, and so on.
In the following description, the turbine vane row 21 will be described as the turbine vane row 21 of a first stage (hereinafter referred to as a first vane row 21) on the most upstream side to which a transition piece 27 of a combustor is connected, and the turbine blade row 22 will be described as the turbine blade row 22 of a first stage (hereinafter referred to as a first blade row 22) adjacent to the downstream side of the first vane row 21.
The first vane row 21 forms an annular shape with a plurality of vanes arranged in the circumferential direction of a turbine. Each of the vanes has a vane main body 21c extending in the radial direction of the rotary shaft, an outer shroud 21a installed at an outer end section in the radial direction of the vane main body 21c, an inner shroud 21b installed at an inner end section in the radial direction of the vane main body 21c, and a retainer 21d protruding inward in the radial direction from a rear surface (a lower side of the drawing) which is a surface inside in the radial direction of the inner shroud 21b. In addition, the first vane row 21 is fixed via a pin 28 to the support ring 25, which is fastened to the intermediate shaft cover 24 by a bolt, such that a downstream surface of the retainer 21d butts against the support ring 25.
In addition, as shown in FIG. 9, the inner shrouds 21b of the vanes of the first vane row 21 are formed in substantially a parallelogram (a diamond shape) when seen in a front view, and connected such that one ends abut each other in the circumferential direction of the axis of the rotary shaft, and slight gaps K are formed between divided surfaces. The vane main body 21c forms an arc shape, and forms a tapered shape in which the width dimension in the circumferential direction is reduced toward the downstream side (the right side of FIG. 8). Further, with its downstream surface butting against the support ring 25, the retainer 21d receives a load in a thrust direction, i.e., the axial direction, due to the differential pressure of a combustion gas G applied to the vane main body 21c, and suppresses displacement of the first vane row 21 in a direction in which it approaches the first blade row 22.
The first blade row 22 forms an annular shape with a plurality of blades arranged in the circumferential direction of the turbine. Each of the blades includes a blade main body 22b extending in the radial direction of the rotary shaft, and a platform 22a installed at the inner end section in the radial direction of the blade main body 22b. Ring segments 29 located at the inner circumference of a turbine casing (not shown) are disposed outside in the radial direction of the first blade row 22 so as to face a distal end of the blade main body 22b. 
Accordingly, the vane main body 21c and the blade main body 22b are disposed in a space surrounded by the outer shroud 21a and the ring segment 29, and the inner shroud 21b and the platform 22a, and this space serves as a main flow path FC1 through which the combustion gas G passes.
Meanwhile, a casing S1 configured to store cooling air exiting the compressor is provided inside in the radial direction of the inner shroud 21b of the first vane row 21. In the inner shroud 21b, in order to separate the main flow path FC1, through which the combustion gas G flows, and the casing S1 from each other, a seal plate 31 is disposed along the divided surface between the adjacent inner shrouds 21b in the axial direction of the rotary shaft, and a seal plate 32 is disposed between the adjacent retainers 21d in the radial direction, thereby closing the gap K. Normally, an air pressure on the casing S1 side is higher than the combustion gas pressure in the main flow path FC1, so that the combustion gas G does not leak into the casing S1.